Making Basic Measurements; Basic Amplifier Measurement - Keysight Technologies N9040B UXA Manual

Making Noise Figure Measurements

Making Basic Measurements

Making Basic Measurements
This section describes how to make basic noise figure measurements, using an
example of a basic amplifier measurement, which performs no frequency
conversion.

Basic Amplifier Measurement

Noise figure measurements are made by measuring the output power of the
DUT for two different input noise power levels. The high and low power inputs
come from a calibrated noise source. The noise source is switched on and off in
rapid succession. High power input to the analyzer uses the noise power
generated when the noise source is switched on, and low power input uses the
noise power generated at ambient temperature with the noise source switched
off.
This section uses a low noise amplifier with a frequency range of 100 kHz to
500 MHz as the DUT and the Keysight SNS Series noise source N4002A to
show how a basic noise figure measurement and various basic operations are
performed. The specifications of interest to the example are listed in the
following table.
Table 2-1 The Example DUT Specifications
Frequency Range
100 kHz to 500 MHz
This example sets a frequency range of interest of 200 MHz to 400 MHz. The
purpose of the measurement is to verify the specified table results are as stated
over the frequency range of interest.
To make noise figure measurements, there are generally two steps:
1. Calibrate the analyzer to measure the noise figure contributed by the
2. Make the measurement with the DUT.
Figure 2-1
measurement. If you are using the Keysight 346x noise source, connect the
NOISE SOURCE DRIVE OUT +28 V (PULSED) port from the rear panel of the
signal analyzer to the noise source instead.
If the DUT has a low or negative gain, it is recommended to use the USB
preamplifier together with the signal analyzer to get more accurate
results. For more details, refer to
Preamplifiers in Noise Figure Measurements" on page
14
Minimum Gain
20 dB
signal analyzer. The calibration used in this example is User Cal.
Two types of calibration are available: User Cal and Internal Cal. See
Cal vs. Internal Cal" on page 59
on page 15 shows the system connections for calibration and
Total Gain range Typical Noise Figure
± 0.5 dB 2.9 dB
for more information.
"Using the U7227-Series USB
37.
N9069C Noise Figure Measurement Guide
"User